The disclosure relates to the operation of a power conversion device and a control circuit at the time of operation stop.
The technology described in Japanese Unexamined Patent Application Publication No. 6-38361 is known as a power conversion device in related art.
The DC/DC converter as a power conversion device described in Japanese Unexamined Patent Application Publication No. 6-38361 is controlled by a microcomputer. A DC voltage is supplied from a commercial AC input to a power source which drives the microcomputer through a transformer, a rectifying smoothing unit, a switch, and a regulator. In order to reduce loss of the regulator, the transformer decreases the voltage of the commercial AC input. The switch is used to stop the operation of the microcomputer. When the output of the DC/DC converter is in an abnormal state, the microcomputer outputs a shutdown signal to the DC/DC converter and the switch to stop the operation of the DC/DC converter and the regulator. The microcomputer performs stop processing by the time when the output of the regulator starts to be stepped down.
However, in a DC/DC converter in related art, the microcomputer has to perform stop processing such as data saving by the time when the output of the regulator starts to be reduced. For this reason, if the time taken for the output of the regulator to start to be reduced is short, the data saving or the like may not be completed. If the data saving is not performed normally, the stop processing of the microcomputer may not be safely performed. To cope with this, the time taken for the output of the regulator to start to be reduced has to be increased, and thus the operation of the DC/DC converter cannot be quickly stopped.
Also, the above-mentioned transformer is a commercial AC transformer, and thus has a large size. In order to reduce the loss of the regulator without using the transformer, when the output voltage of the DC/DC converter is low, connecting the input of the regulator to the output voltage of the DC/DC converter reduces the loss. However, when the output of the DC/DC converter is lowered due to an operation of protection against overheat of the DC/DC converter, the power source of the microcomputer is reduced in power, and the microcomputer may not be able to safely perform the stop processing such as data saving. The DC/DC converter needs a function similar to the function of the regulator which supplies a power source to the microcomputer, and this leads to increase in chip size.